In most, if not all, known wire carriers, the carrier is comprised of a continuous length of stiff metal wire bent to and fro into a zig-zag formation, with looped wire edge regions and transverse lengths of wire in a central region of the carrier joining the wire loops in the edge regions. The transverse lengths of wire may be straight or curved, the curved variety being either banana shaped or propeller shaped, or a combination of straight and/or banana shape and/or propeller shape. The zig-zag wires are stayed and maintained in their spaced relation with each other by a plurality of strands of material extending lengthwise of the carrier, parallel to its edge, and connected to each transverse length of wire and/or the loops by knitting the strands into the zig-zag wire, so as to provide a stitch, or knot at each crossing point. The end product is known as a knitted wire carrier and is clearly illustrated in GB-A-1407412 or U.S. Pat. No. 3,198,689. The lengthwise strands are important to prevent stretching and shrinking of the product in which the carrier is to be used.
The knitted wire carriers disclosed in the above mentioned specifications have lengthwise strands formed of textile material, such a polyester, cotton or the like, or even light wire, and traditionally have been used for many years in the manufacture, inter alia, of edge trim or combination edge trim door (or boot) seals for motor vehicles. These are formed by extruding a polymer material onto the wire by passing the latter through an extruder, and then forming the resultant product into a generally U-shape (although in some instances the knitted wire carrier can be pre-formed into a U-shape and passed through an extruder with a generally U-shaped die).
Door seals on motor vehicles have traditionally been held in place in the door openings (or on the door) by gripping onto the manufacturer's metal flanges around the door openings (or door), although other systems are now being developed. With the ever increasing complexity in motor vehicle manufacture, and in particular, the ever increasing customer requirement for efficient, good looking door seals in motor vehicles, it is important the door seals fit correctly and do not fall off or become displaced. If they do become displaced even by a small amount, they will look unsightly, will affect door shut pressures, and will also not form a satisfactory air/water seal between the door and door opening.
Modern motor vehicles tend to be manufactured with a distinct waistline (belt line) half way up the body, at approximately door lock height, and this results in two changes of direction in the flange to which the edge trim/door seal is to be fitted. Furthermore, with the advent of small motor vehicles, the sealing strip is required to negotiate sharp inside and outside bends, as well as lateral bends at the waistline, and yet still maintain its correct location on the flange, in spite of regular opening and shutting of the door. Although the whole purpose of knitted wire carriers in extruded edge trims is to stiffen the polymeric material of the extrusion, there is nevertheless now a requirement for local flexibility and variable stiffness in the carrier so that the edge trim can negotiate the various bends satisfactorily. It must also be borne in mind that when the edge trim is bent, especially if it has a door seal attached or integral therewith, then the polymeric material may deform, or wrinkle or buckle, as a result of stretching, twisting or compression, thus resulting in an ugly appearance. To a large extent, these deficiencies can be minimised or avoided by designing the stiffness of the knitted wire carrier accordingly, e.g. by making selected regions of the carrier stiffer than others, either along the length of the carrier, or across its width.
Various attempts to vary the stiffness of wire carriers have been proposed, and these proposals have met with different levels of success. For example, in EP-B-0155811, a knitted wire carrier is disclosed wherein at least two different zig-zag wires are incorporated in the carrier. In another construction disclosed in EP-B-0045176, two different types of textile material are used for the knitted longitudinal strands, one of the materials being degradable so that when a controlled amount of heat, or radiation, or other means is applied to the edge trim or the like in which the knitted carrier is located, the one material can be degraded so that it will no longer inhibit relative movement of the transverse lengths of wire in the carrier, and will thus cause a change in the stiffness of that region of the carrier.
The above-mentioned attempts to vary the stiffness of the carrier suffer from one disadvantage, namely that it is difficult to vary the carrier stiffness or flexibility across the width of the carrier, because throughout its length, the carrier is formed of uniform construction.
The present invention seeks to overcome this disadvantage. While it is specifically concerned with knitted wire carriers, it could be incorporated in non-knitted, e.g. woven wire carriers, or in what are known as slotted metal carriers, i.e. ones not made of wire, but of stamped, pressed, or formed metal, or in carriers of other material.
In GB-A-964605, various constructions of slotted metal carrier are disclosed, which are designed so that door seals or trims in which they are incorporated can negotiate sharp bends without unsightly distortion of the trim, and without any impairment of the gripping action which is effected by the carrier. In some of the constructions of carrier disclosed, the spaced transverse members of the slotted metal carrier are connected by means, i.e. bridging ribbons, the transverse position of which vary uniformly throughout the length of the carrier. In each of these different constructions, the carrier will itself have, and provide the trim with, uniform characteristics throughout its length. This means that the trim may be ideal for negotiating, for example, internal bends on a flange defining a door opening, but not suitable for negotiating bends extending in several different planes, and perhaps also internal and external (i.e. convex and concave) bends.